The University of Dayton (UD) is a private, Catholic research university in Dayton, Ohio. Founded in 1850 by the Society of Mary, it is one of three Marianist universities in the nation and the second-largest private university in Ohio. The university's campus is in the city's southern portion and spans 388 acres on both sides of the Great Miami River. The campus is noted for the Immaculate Conception Chapel and the University of Dayton Arena.